The present invention relates to a fiber-reinforced material composed of a sheetlike textile material composed at least in part of synthetic fibers and a fluoropolymer-containing thermoset resin, a prepreg for producing the fiber-reinforced material, and sheetlike or three-dimensional construction elements formed therefrom.
It is already known to manufacture construction elements such as guide and sealing collars and rings as preferred in hydraulic systems from thermosetting resins reinforced with cellulose fiber fabric (fabric-based laminate tape). However, these known construction elements are insufficiently flexible in practice; they frequently tend to delaminate and cause excessively high friction losses in various applications. Similarly, the heat resistance of these construction elements frequently leaves something to be desired in practice.
Considerable problems arise with guide rings specifically in hydraulic systems owing to the combined effect of high static and dynamic pressures, transient high edge loads and high working temperatures at the same time as the constant abrasive stress due to the gliding movements of the hydraulic elements in the presence of the swelling and solubilizing hydraulic fluid.
Guide elements made of a thermoplastic material which per se have good gliding and flexing properties and are more resistant to transverse forces, as may arise for example in the event of high edge loads, than more brittle materials quickly fail in hydraulic systems under the above-described working conditions. At low temperatures, as may arise for example in the winter operation of hydraulic systems, they become brittle, so that they are also easily destroyed by edge loads; at increasing temperatures they undergo plastic deformation.
It is also already known to use composite materials formed from metal powders and polytetrafluoroethylene for manufacturing slide and guide rings in order to exploit the good frictional properties of polytetrafluoroethylene.
However, under the high pressures of modern hydraulic systems these materials exhibit excessively high cold flow, so that they are not even usable at standard temperature, let alone under the customary operating temperatures of these systems.
British Patent 974,629 discloses a process of manufacturing bearings using a material comprising a thermosetting resin reinforced with a fabric strip. To reduce the friction losses on using these known bearing elements, polytetrafluoroethylene powder is embedded in the surface of the material in the course of the forming process.
British Patent 1,031,406 discloses a composition for producing low friction coefficient protective coatings on substrates such as wood or steel. This composition consists essentially of a curable resin, for example a thermosetting phenol-formaldehyde resin, which contains low molecular weight fluoropolymers in finely divided form.
A similar composition for producing low friction coefficient protective coatings and a process therefor are disclosed in German Patent 1,250,035.
The present invention, then, provides a fiber-reinforced material from which it is possible to produce construction elements having a relatively low friction coefficient and a high pressure and abrasion resistance, appreciably improved flexibility, extensibility, shear resistance and delamination resistance and high temperature resistance and which at the same time are inert toward solubilizing and/or swelling fluids, for example hydraulic or lubricating fluid, and which therefore are suitable for use in particular for example as guide elements in highly sressed hydraulic systems or for fabrication of bearings, in particular slide bearings.